For current cavity pole designs, RIE (Reactive Ion Etching) and Al2O3 are used to create the pole mold, including a bevel angle. One process phenomenon is that the bevel angle in the yoke area is greater than in the pole area (due to etch area differences). This, however, causes the NH (Neck Height) to be much longer at the bottom of the pole than at its top. Also, the magnetic volume at the flare point is significantly reduced. All of which will impact the head's writing performance.
FIGS. 1a-1d illustrate this problem. FIG. 1a is a plan view of a mold which will be used to form the write pole. Line 15 indicated the plane of the ABS (air bearing surface in the completed device). Neck height is the distance from the ABS to the flare point. In a typical mold formed using the methods of the prior art, it will be longer at the floor than at the top of the cavity
FIG. 1b is an isometric view of FIG. 1a. Section cut 1c-1c corresponds to line 15 in FIG. 1a while layer 42 is a hard mask of tantalum that was used during RIE (reactive ion etching) to form the pole tip portion of mold area 61. FIG. 1d shows one of the sidewalls 16 in the tip area, illustrating how it slopes, at angle 17 (typically between about 7 and 12 degrees), at the flare point which results in the longer neck height B at the bottom of 61 relative to neck height A at the top.
This invention describes a new process to reduce the bevel angle in the yoke area while continuing to maintain the angle at the pole tip area, thereby resulting in a neck height that is the same at both levels. A routine search of the prior art was performed with the following references of interest being found:
U.S. Pat. No. 6,614,620 (Tagawa et al) describes using Al2O3 to etch the pole. In U.S. Pat. No. 6,510,024, Otsuka et al. disclose Al2O3 or other low etch rate material used to form the recording gap. U.S. Pat. No. 6,854,175 (Sasaki) shows that tantalum can be used in addition to alumina for the write gap layer while U.S. Pat. No. 6,504,675 (Shukh et al) discusses the slope angle of the pole sides.
U.S. Patent Application 2004/0175596 (Inomata et al) shows a tantalum protective layer on top of a stack including Al2O3. U.S. Patent Application 2002/0041465 (Sasaki) shows tantalum on alumina and RIE to form the pole. U.S. Pat. No. 4,672,493 (Schewe) and U.S. Pat. No. 4,656,546 (Mallory) disclose magnetic recording head pole designs.